[SPARK-11925][ML][PYSPARK] Add PySpark missing methods for ml.feature during Spark 1.6 QA

Add PySpark missing methods and params for ml.feature:
* ```RegexTokenizer``` should support setting ```toLowercase```.
* ```MinMaxScalerModel``` should support output ```originalMin``` and ```originalMax```.
* ```PCAModel``` should support output ```pc```.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #9908 from yanboliang/spark-11925.